While designing integrated circuit boards for electronic systems, such as computers, most designers feel uneasy about the operation of the circuit boards which are apt to be badly effected by heat. That is, when the temperature around an integrated circuit board for electronic systems rises to a high point, the circuit board may be badly affected by heat and this causes the signal-up/down timing of the circuit board to be thermally changed from a designed timing. In such a case, the circuit board may malfunction. Particularly in the case of a digital circuit board for electronic systems, heat may change the designed signal-up/down timing of the circuit board and this prevents the circuit board from exactly sending or receiving signals.
Since CPUs (central processing units) for portable computers, such as laptop computers, notebook computers or palmtop computers, are highly integrated and miniaturized, it is necessary to design such CPUs so that they effectively dissipate heat to the surroundings during their operation.
Typical methods of dissipating heat from circuit boards for electronic systems to the surroundings are accomplished by indirect cooling apparatus, which are added to the systems and indirectly dissipate heat from the circuit boards to the surroundings. That is, heat sinks, heat pipes and/or motored fans are typically used for indirectly dissipating heat from circuit boards of electronic systems to the surroundings. Such heat sinks, heat pipes and motored fans are selectively installed in electronic systems to cooperate with each other for cooling the circuit boards of the systems. However, such an indirect cooling apparatus is problematic in that it may fail to effectively cool such circuit boards.
Examples of known cooling apparatus are: U.S. Pat. No. 5,796,580 to Toshihiro Komatsu et al., entitled Air-Cooled Information Processing Apparatus Having Cooling Air Fan, Sub-Fan, and Plural Separated Cooling Air Flow Channels; U.S. Pat. No. 5,740,013 to Arlen L. Roesner et al., entitled Electronic Device Enclosure Having Electromagnetic Energy Containment And Heat Removal Characteristics; U.S. Pat. No. 5,737,171 to Marvin Lawrence Buller et al., entitled Switched Management Of Thermal Impedence To Reduce Temperature Excursions; U.S. Pat. No. 5,734,550 to Mark B. Penniman et al., entitled Computer Having A Heat Transfer System Operably Connected During Assembly of a Computer Keyboard Upon The Computer; and U.S. Pat. No. 5,729,431 to Ramesh Marwah et al., entitled Heat Sink For A Portable Personal Computer.